Hi,

From your screen shot, it looks like you may have already done some transactions to/from this warehouse.  The option to choose Consigned/Reserved is also disabled which happens when there are products already in the warehouse and this disables the owner selection.  In this case, no you cannot change the warehouse to consigned with an owner while there are products associated to any of the non-consigned bins in the warehouse.

I created a normal warehouse populated some products with a miscellaneous receive into the default good bin and the option to choose consigned was disabled as was the owner just like your screenshot.

However, if I removed all the products from the warehouse (In my case, I did a manual adjustment) and then removed the bin-product relationships with the Empty Bins Removal Batch for that warehouse, the option to choose consigned became available again.

At this point, to enable the consignment owner, you need to define consigned bins in the warehouse such as these before selecting the consigned option for the warehouse & choosing an owner.

Which will then enable the consignment owner field for selection:

After this, select your owner the lookup making sure the company selected is defined previously as using consigned stock in their attributes.

After selection & save, you should have something like the below and it should be a consigned warehouse.

The point is, there cannot be any products in the warehouse in bins that are not consigned nor bin-product relationships.  Otherwise you cannot convert the warehouse to a consigned warehouse.

Hope this helps.